Disposable plastic knife



FIG. 1 is a bottom, right side elevation view of a disposable plastic knife, showing my new design;

FIG. 2 is a right side elevation view thereof, where the left side elevation view is a mirror image of the right side elevation view;

FIG. 3 is a rear view thereof;

FIG. 4 is a top view thereof; and,

FIG. 5 is a bottom view thereof.

The broken line portion of the figure drawings is included to show unclaimed subject matter only and forms no part of the claimed design. 

The ornamental design for a disposable plastic knife, as shown and described. 